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Paul McGowan weighs in on uncompressed vs lossless compression

bencat

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Okay sort of get the point but what would not just using a better specified LPSU which many of us do solve the power issue ? Also and I have never been quite sure of this I have my LMS on a stand alone Pi which runs LMS and has a HD connected . It sends any music over the the network by ethernet cable . Does the server decompress the Flac file and send the data as a pcm stream or does it send the flac file as it is and player then decompresses the file and plays it ? If it is the first then the power supply issue should be solved as it is sending an identical digital file as the original WAV file to the player and then playing it .

 

Warszawa

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My opinion on this is has always been that if you can hear a difference between lossless compression and uncompressed files, your streamer is to blame, not the codec.
 

Also, you can add metadata to .wav files. 

 
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Jules_S

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My opinion on this is has always been that if you can hear a difference between lossless compression and uncompressed files, your streamer is to blame, not the codec.
 

Also, you can add metadata to .wav files. 
Did you mean "can't" rather than "can"? I've never found a way to add metadata to WAV, although in the past when I used to use iTunes you could certainly create metatdata and attach it, but that was iTunes own internal database and not actually part of the WAV file itself.

I'm hardly an authority on the subject but I would agree with your opinon about the device doing the decompression being responsible for any differences between lossless compressed and normally-uncompressed files. Surely the whole point of lossless is that the results of the compression / decompression process results in a file that is identical to the original? So to my mind the file format itself can't be responsible; any differences in the output must be down to the inability of the device doing the processing to complete the decompression accurately.

Are there uncompressed file formats that support metadata? I'm not familiar with DSD  - does that count?

 

Warszawa

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You can add metadata to WAV. Most modern streamers support it.

 

Jules_S

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Well that's something new I've learned today :)  I expect it may be down to the equipment I've been using then, i.e. my car audio, as that's one of the few situations when I have tried using WAV.

 

andrew s

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 Obviously the solid state or hard drive has to do more work retrieving an uncompressed file. So it's a trade off between dive and CPU the impact of which I have no idea on power usage, network and bus loading or audibility. 

Regards Andrew 

 
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Shadders

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Does the server decompress the Flac file and send the data as a pcm stream or does it send the flac file as it is and player then decompresses the file and plays it ?
Hi,

The server will decompress the file and then send the bit stream to the DAC. The AES/SPDIF standard does not allow for FLAC compressed files.

FLAC lossless is, lossless. If there are any decoding errors, then the file will not play, or the sound will be completely ruined (dangerous for speakers, potentially). There will be no subtle changes in sound which may indicate that the decompression process is not working optimally. It either works or it doesn't, no in betweens.

Regards,

Shadders.

 

DomT

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I have been looking for some articles on this subject and can’t find a single one. Not even Wiki FLAC page has info. Seems crazy that there is no documented info on how and where FLAC is unpacked and if and how it might cause audio problems. 

 

cynix

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I've been ripping to WAV's since the Squeezebox touch first appeared and metadata is usually added directly to the files automatically when ripping with Windows Media Player. Where it has to be done manually or edited later I use "Stamp" from NCH software :

https://www.nch.com.au/tageditor/index.html

The metadata is recognised by the SBT and a Cambridge Audio Minx XI no problem, using Logitech Media Server.

 

Shadders

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Thanks but there doesn’t seem to be any info on this specific topic. Maybe you could point to exactly where it is?
Hi,

The page :

https://xiph.org/flac/documentation_format_overview.html

Has more information on the encoding process. Decoding is the reverse operation. There are no errors or audio issues. Any implementation either works or it does not.

The DAC IC's are not able to decode FLAC files, nor can the FLAC file data stream be transmitted along the SPDIF to the DAC. As such, all processing of FLAC has to be implemented in the streamer. This process can be in software for OS embedded type streamers, or a specific IC as per the cheaper streamers or media centres (sigma designs processor).

Regards,

Shadders.

 
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tuga

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Unless you have a massive amount of music files that makes storage impractical or overly expensive then I see no reason for using a losslessly compressed format (e.g. FLAC, ALAC), even if the effects of an on-the-fly decompression issue are negligible.

AIFF can store both metadata and cover image.

 

Camverton

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I've been ripping to WAV's since the Squeezebox touch first appeared and metadata is usually added directly to the files automatically when ripping with Windows Media Player. Where it has to be done manually or edited later I use "Stamp" from NCH software :

https://www.nch.com.au/tageditor/index.html

The metadata is recognised by the SBT and a Cambridge Audio Minx XI no problem, using Logitech Media Server.
Thanks, interesting range of software. I’m a bit confused as in their faqs they state:


Why can't I tag my wma/wav/acc file?


WMA has its own tagging format, which is specified in the wma spec and does not allow open source implementations, WAV files do not contain tags and AAC uses another tagging format with no published specification.

Are you sure that you are writing to tags in the actual wav file rather than a sidecar file or database?

 

DomT

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Hi,

The page :

https://xiph.org/flac/documentation_format_overview.html

Has more information on the encoding process. Decoding is the reverse operation. There are no errors or audio issues. Any implementation either works or it does not.

The DAC IC's are not able to decode FLAC files, nor can the FLAC file data stream be transmitted along the SPDIF to the DAC. As such, all processing of FLAC has to be implemented in the streamer. This process can be in software for OS embedded type streamers, or a specific IC as per the cheaper streamers or media centres (sigma designs processor).

Regards,

Shadders.
This document does not mention decoding at all and nor does it mention ANY of the points in your response. (And some streamers send data via USB to a DAC). 

We need to read a technical specification document describing it rather than the opinion of a guy in the internet. But of course if you did write the FLAC technical spec please give us a link to your document. 

 

Shadders

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This document does not mention decoding at all and nor does it mention ANY of the points in your response. (And some streamers send data via USB to a DAC). 

We need to read a technical specification document describing it rather than the opinion of a guy in the internet. But of course if you did write the FLAC technical spec please give us a link to your document. 
Hi,

For a lossless system, the encoding is reversed to obtain the lossless data, hence decoding is the reverse of encoding. Same for data file compression using ZIP format or other, nothing can be lost, so the lossless decoding is the same process as encoding, but reversed. This is also true for symmetrical data encryption on hard disks, the algorithm is deterministic, else you would lose data in decryption.

When you send data via USB, there may be an interface that can accept FLAC. Many DAC designs use the XMOS solution, and i don't think they decode FLAC on their board or IC.

Regards,

Shadders.

 

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